Subject: pruning required in mrouted ?

From: Andrew Daviel <[email-masked]>
Date: Tue, 12 Oct 1999 13:54:39 -0700 (PDT)

We are basically a leaf node on the Mbone. We had been running
mrouted 3.8 on an SGI but it has been a bit unreliable, and I am
considering using our FORE PowerHub 7100 directly.

The PowerHub is an older model; according to mrinfo it is running "version
2.0". Thus, I believe it is not running prune and is not trace-capable. A
software upgrade may be impossible without replacing some hardware.

Is pruning absolutely required everwhere, or just at routing nodes?
I haven't been following the list for a while; I remember some push to
make sure no-one ran mrouted3.7.

Would it cause trouble if we enable multicast on this router ?

Andrew Daviel
TRIUMF

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From: "Alan J. Flavell" <[email-masked]>
Date: Thu, 21 Oct 1999 21:50:27 +0100 (BST)

Hello there...

On Tue, 12 Oct 1999, Andrew Daviel wrote:

> Is pruning absolutely required everwhere, 

I think the answer is basically "yes", though there might be some
exceptional situations.

I'm not sure what kind of multicast support your router is offering. I
guess we both started this at a time when DVMRP with IP-in-IP tunnels
was the only way, but there's all kinds of different ways nowadays!

> or just at routing nodes?

No, a non-pruning leaf node can do just as much harm, as far as I
know.

> make sure no-one ran mrouted3.7.

Even 3.8 is buggy, especially in the face of routing instabilities: NB
those instabilities need not be anywhere close to the v3.8 mrouted -
we found all kinds of leakage until we moved to the so-called
3.9beta3, associated with routing instabilities that, as far as we
could tell, were entirely outside of the UK.

> Would it cause trouble if we enable multicast on this router ?

I recommend keeping a close eye on the multicast traffic levels if you
try it.  It's easiest if you have an SNMP-capable mrouted upstream, so
that you can graph its multicast traffic to check what's going on.  
If not, then use mtrace to investigate the aggregate packet rates.

May I suggest you contact me off the list if you're interested in this
issue, and we can report a summary back to the list.

Disclaimer: I'm not an expert in these matters, but I do know a few
of them, and I run an mrouted myself for the Physics dept.

p.s I get excellent results with a quite elderly PC dedicated to 
running mrouted under FreeBSD.